In an existing packet-switched communications network, a forwarding path must be set up between network nodes to forward service packets. A forwarding path is implemented through a tunnel management procedure, and is created or updated between network elements through a tunnel management request. However, it is possible that the tunnel management request fails for certain reasons. For example, an error occurs in the request message or resources of an associated network node are exhausted. In a prior art, a cause value is generally used to indicate the processing result of the tunnel management request. The cause value indicates whether the processing of the tunnel management request succeeds or fails and indicates the reason of failure when the tunnel management request fails.
In an evolved packet system (EPS), when the mobility management element is a mobility management entity (MME), signaling exchanged between the MME and a packet data network gateway (PDN-GW or P-GW) must cross a serving gateway (S-GW). When a mobile terminal initiates a mobility management or session management procedure that includes a tunnel management request, such as an EPS attach, routing area update, tracking area update, handover, or external PDN connectivity procedure, the MME sends a tunnel management request and the S-GW and PDN-GW cooperate to process the tunnel management request. No matter whether the processing of the tunnel management request is successful or not, the S-GW will send a response which includes a cause value to the MME, indicating the processing result to the MME.
In the tunnel management procedure, however, the inventor finds at least the following problem in the prior art:
If the tunnel management request fails, the node that initiates the tunnel management request receives a response but cannot determine the error of which node has caused the tunnel management request failure according to the response. As a result, the node that initiates the tunnel management request cannot perform processing according to the tunnel management failure caused by different nodes.